Seasonal Physical Fronts and Associated Biogeochemical‐Ecological Effects off the Jiangsu Shoal in the Western Yellow Sea, China

Abstract

AbstractThe Jiangsu Shoal and its adjacent area in the western Yellow Sea (YS) have become hotspots of ecological disasters in China and have attracted considerable attention. Based on remote sensing and field observations in this region, we investigated the physical fronts and their seasonal variations and clarified the spatiotemporal patterns of physical‐biogeochemical factors as well as their interactions and synergies. The results show that pronounced physical fronts were present in the study area. Specifically, arc‐ and “S”‐shaped thermal fronts existed off the shoal in summer and winter, respectively. The saline front largely expanded southeastward in spring, autumn, and winter, while it expanded northeastward in summer. The turbidity over the shoal was high year‐round, and a marked turbidity front was formed between the nearshore water and the offshore seawater. The seasonal patterns and variations of the physical fronts significantly influenced material transport. During cold seasons, the frontal system was responsible for the significant turbid water plume expanding in a southeastern direction from the Jiangsu Coast. In summer, the arc‐shaped thermal front confined the turbid water within the shoal. The expansion of excess dissolved inorganic nitrogen was consistent with the saline front, and the vertical transport of nutrients by upwelling occurred off the shoal in summer. Due to favorable conditions, the frontal region off the shoal is prone to high chlorophyll a (Chl‐a) and may act as oases in either summer or winter. A conceptual diagram is assembled to provide an overview of physical‐biogeochemical‐ecological interactions off the Jiangsu Shoal in the western YS.